(1) Field of the Invention
The present invention relates to a pump motor and its internal construction. The pump motor has a permanent magnet rotor, a containment shell, a wound stator, a motor housing, a pump head, and a shaft, which is secured in the containment shell on the one hand and in the pump head on the other hand, and a fixed bearing, which is pressed or injected into the permanent magnet rotor and rotatably mounts it on the shaft.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 197 and 1.98
In combustion engines of motor vehicles, mechanical pumps driven by the crankshaft via a gear belt are generally provided as main cooling water pump. As a support or an alternative in a shut-off combustion engine, electric ancillary cooling water pumps are used, which are generally designed as electronically commutated direct-current motors. Main cooling water pumps can also be operated electrically. From DE 10 2011 079 226 B4 is known a generic pump, in which bearing bushes are used to mount the permanent magnet rotor on the shaft. In doing so, a running surface of the bearing can be deformed by a press-fitting process of the bearing bush into the permanent magnet rotor such that punctual or linear contacts of the bush with the shaft result. This effect is particularly pronounced in bearing bushes with different material thicknesses, as is the case in collar bushes. Such deformations generally result in increased bearing noises. For economic reasons, the tolerances for bearing bushes cannot be arbitrarily small, which is why undefined bearing pairings can occur, in which the shaft abuts non-uniformly over the bearing length and non-uniformities also occur during a rotation.